President Obama will challenge companies Thursday to expand their use of solar power, part of his ongoing effort to leverage the power of his office to achieve goals that have been stymied by Congress. The new initiative comes as the White House is hosting a Solar Summit aimed at highlighting successful efforts on the local level to speed the deployment of solar energy.

Although some large solar plants are coming online and it is the fastest-growing source of renewable energy in the United States, according to the U.S. Energy Information Administration, it accounts for roughly 1 percent of the nation’s electricity generation.

“Now is the time for solar,” said Anya Schoolman, executive director of the Community Power Network, a Washington-based nonprofit group that helps communities build renewable energy projects. She will be honored at the summit Thursday.

“The costs are affordable, in reach of middle America and above. We know how to do it now, we know how to scale it, and we kind of just need people to let it go and encourage it,” she said.

In an effort to make it easier for state, local and tribal governments to expand their solar portfolios, the Energy Department is launching a $15 million-dollar “Solar Market Pathways” program.

Another branch of DOE, along with the National Renewable Energy Laboratory, is also going to lend its staff and expertise to ensure that the administration meets its goal of having 100 megawatts of renewable energy installed on-site at federally subsidized housing by 2020. The Defense Department, the nation’s largest energy consumer, has one of the government’s most ambitious renewable goals: deploying 3 gigawatts on military installations by 2025. As part of that effort, on April 25 the Army will break ground on a solar array that will provide nearly a quarter of the annual electricity required for Fort Huachuca, Ariz.

Energy Secretary Ernest Moniz and White House counselor John D. Podesta will announce the new solar initiatives, including the president’s call for new private sector commitments, at the White House summit Thursday.

Schoolman said a suite of federal and, in many places, state tax credits have made installing solar much more affordable now than even a few years ago. The average price of solar panels has dropped more than 60 percent since 2010, according to the White House.

But those incentives most benefit individual homeowners, who still can wait years to recoup their investment. Owners of large structures, especially those in states where electricity costs are high, don’t benefit as easily, especially those buildings used for affordable housing.

Elyse Cherry, chief executive of Boston Community Capital, which finances community development, said the tax credits don’t work for affordable housing, because the up-front costs are so high and cost-savings is realized over such a long period of time.

Cherry said she is “delighted” that the White House is focusing on making it easier for nonprofit groups and tenants in affordable housing to access solar energy.

“We think lower-income communities are entitled to exactly the same services and availability to technology and energy sources as their wealthier neighbors,” she said.

States are starting novel ways to help commercial tenants access solar energy. In Connecticut, the state set up a green bank with taxpayer dollars. When a building owner wants to access capital for solar projects, the state puts a tax lien on the building and gives the owner a loan that must be paid back over 20 years, said Jessica Bailey of the Connecticut Clean Energy Finance and Investment Authority.

The federal government has done a poor job of creating a consistent solar policy, Bailey said, but she is happy that Obama’s commitment to solar is “getting stronger and deeper.”

Rhone Resch, president and chief executive of the Solar Energy Industries Association, a trade group, said solar is no longer an “afterthought” in the renewable energy conversation, accounting for nearly 30 percent of new electric in 2013.

“Without question, the Obama administration has been the most solar-friendly ever,” Resch said.